I went back and looked at the Gunbroker rifle. While I can't see the period in the photo, the spacing of the M1 is actually M 1, identical to mine, so it will probably be 30/25 M.1 if that makes a difference to anybody.
Additional observations:
It has a Service Rifle barrel on it, so this MAY have been a National Match rifle. You can see that from the filling in of the rear sight collar pin.
The original USGI serial number SHOULD be on the bottom of the receiver, if anybody cared to ask.
The front sight hood is incorrect, as is the stock and recoil pad.
The front sight itself is correct, and all the other metalwork appears to be.
As far as the price................................
